Through talking to scientists who build and use computer simulation, I am investigating the roles of this type of representation in the production of knowledge. I am addressing questions like: what constitutes a realistic simulation? In what sense can a computer program represent reality? How does simulation fit into traditional classifications of scientific method? Rather than taking a traditional "armchair philosophy" approach to these questions, I am visiting laboratories in a variety of fields, to look at applications of computer simulations and study scientists' own understandings of the role of simulation in the production of knowledge. I used the resources in the Computer Graphics Lab simply to get a visual and experiential impression of this type of computer simulation. The experience gave me a deeper understanding of the perspectives of the scientists I talk to.